Glass fiber

ABSTRACT

There is provided a glass fiber comprising the SiO 2  content is 57.0 to 63.0% by weight; the Al 2 O 3  content is 19.0 to 23.0% by weight; the MgO content is 10.0 to 15.0% by weight; the CaO content is 4.0 to 11.0% by weight; and the total content of SiO 2 , Al 2 O 3 , MgO and CaO is 99.5% by weight or higher based on the total weight.

TECHNICAL FIELD

The present invention relates to a glass fiber, particularly ahigh-elasticity glass fiber.

BACKGROUND ART

As a glass for a glass fiber excellent in strength and elastic modulus,a glass (S glass) composed of a glass composition of SiO₂, Al₂O₃ and MgOis conventionally known. However, with respect to the S glass, theproduction of the glass fiber is not always easy from the viewpoint ofthe 1,000-poise temperature and the liquid phase temperature. Here, the1,000-poise temperature refers to a temperature at which the meltviscosity of a glass becomes 1,000 poises, and the liquid phasetemperature refers to a temperature at which the crystal depositiontakes place for the first time when the temperature of a molten glass isdecreased. Generally since glass fibers can efficiently be produced inthe case where glass is spun by making the melt viscosity of the glassnearly 1,000 poises, spinning is usually carried out in the temperaturerange (working temperature range) between the 1,000-poise temperatureand the liquid phase temperature. With respect to the S glass, theworking temperature range is narrow, and the molten glass is liable tocrystallize (devitrify) even under an influence of only a slighttemperature decrease. Therefore, in order to carry out stable spinning,in the production step of glass fibers, the spinning condition needs tobe precisely controlled.

As an improved S glass, glass compositions containing SiO₂, Al₂O₃, MgOand CaO are known (Patent Literature 1 and Patent Literature 2 shownbelow). Patent Literature 1 discloses a glass composition easilyfiberized along with a decrease in the liquid phase temperature. PatentLiterature 2 discloses a glass composition in which a difference islarge between a temperature (fiberization temperature) corresponding tothe viscosity of a near 1,000-poise temperature and a maximumtemperature (liquidus) at which an equilibrium is present between aliquid glass and a primary crystal phase thereof.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Examined Patent Application PublicationNo. 62-001337

Patent Literature 2: Japanese Unexamined Patent Application PublicationNo. 2009-514773

SUMMARY OF INVENTION Technical Problem

However, studies by the present inventors have revealed that althoughglass compositions of Patent Literatures shown above had a somewhatbroad working temperature range, there are some cases where the1,000-poise temperature and the liquid phase temperature are high, andthe production of glass fibers is not always easy. There has beenrevealed also a tendency that the elastic modulus of glass fibersobtained was insufficient.

Then, the present invention has been achieved in consideration of suchproblems of conventional technologies, and has an object to provide aglass fiber which is easily produced and has a sufficient elasticmodulus.

Solution to Problem

In order to achieve the above-mentioned object, the glass fiberaccording to the present invention has a composition in which, the SiO₂content is 57.0 to 63.0% by weight; the Al₂O₃ content is 19.0 to 23.0%by weight; the MgO content is 10.0 to 15.0% by weight; the CaO contentis 4.0 to 11.0% by weight; and the total content of SiO₂, Al₂O₃, MgO andCaO is 99.5% by weight or higher based on the total weight. Since havingsuch a composition can reduce the 1,000-poise temperature and the liquidphase temperature, the production of the glass fiber from the glasscomposition is easy. Additionally, the glass fiber results in having asufficient elastic modulus.

In the composition of the above glass fiber, the total content of thecontents of SiO₂ and Al₂O₃ is preferably 77.0 to 85.0% by weight. If thetotal content is 85.0% by weight or lower, since the 1,000-poisetemperature and the liquid phase temperature can be reduced, theproduction of the glass fiber from the glass composition is easy. Bycontrast, if the total content is 77.0% by weight or higher, since thedevitrification phenomenon of deposition of crystals in the glass hardlyoccurs, spinning becomes easy in the production.

Further in the composition of the above glass fiber, the weight ratio ofthe SiO₂ content/the Al₂O₃ content is preferably 2.7 to 3.2. If theratio is in such a range, the glass fiber results in having a broadworking temperature range in the production, and having a sufficientelastic modulus.

Further in the composition of the above glass fiber, the total contentof the MgO content and the CaO content is preferably 16.0% by weight orhigher. In this case, since the 1,000-poise temperature and the liquidphase temperature of the glass composition, which is a raw material ofthe glass fiber, are low and additionally the viscosity of the moltenglass decreases, and thereby the glass composition easily melts, theproduction of the glass fiber from the glass composition becomes easier.

Further in the composition of the above glass fiber, the weight ratio ofthe MgO content/the CaO content is preferably 0.8 to 2.0. If the weightratio is 2.0 or lower, since the liquid phase temperature decreases, theworking temperature range in the production can be broadened. Bycontrast, if the weight ratio is 0.8 or higher, the glass fiber resultsin having a sufficient elastic modulus.

The present invention also provides a glass fiber having a compositionin which the three components SiO₂, MgO and CaO out of constituents ofthe glass fiber satisfy the condition being in the range surrounded bycoordinate points described below in a three-component phase diagramrepresented by coordinates ((a), (b), (c)) in which (a) the SiO₂content/(the SiO₂ content+the MgO content+the CaO content)×100, (b) theMgO content/the SiO₂ content+the MgO content+the CaO content)×100, and(c) the CaO content/(the SiO₂ content+the MgO content+the CaOcontent)×100 are taken as respective coordinates, the coordinate pointsbeing ((a)=81.0, (b)=19.0, (c)=0.0), ((a)=71.0, (b)=29.0, (c)=0.0),((a)=71.0, (b)=15.0, (c)=14.0) and ((a)=81.0, (b)=8.0, (c)=11.0).

The present inventors have found that by making a crystal(devitrification primary phase) formed first in devitrification of theglass to form a cordierite crystal or a mixed crystal of cordierite andanorthite, the devitrification speed can be suppressed. Particularly inthe case where Al₂O₃ is made nearly 20% by weight, by making the abovecondition of the three-component phase diagram to be satisfied, thedevitrification primary phase becomes a cordierite crystal or a mixedcrystal of cordierite and anorthite. Therefore, a glass fiber havingsuch a composition, even in the case where the working temperature rangein the production cannot sufficiently be broadened, becomes easy toproduce without causing devitrification, and furthermore results inhaving a sufficient elastic modulus.

Advantageous Effects of Invention

The present invention can provide a glass fiber which is easily producedand has a sufficient elastic modulus by having a specific composition.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a composition diagram showing three-component compositions ofSiO₂, MgO and CaO of glass fibers.

FIG. 2 is a composition diagram showing three-component compositions ofSiO₂, MgO and CaO in the case where the Al₂O₃ content of the glassfibers is fixed at 20% by weight.

DESCRIPTION OF EMBODIMENTS

The composition of the glass fiber according to the present embodimentis a basic composition containing SiO₂, Al₂O₃, MgO and CaO, and thecontent of each component is in the following range. The content isbased on the total weight of the composition of the glass fiber.

(1) SiO₂: 57.0 to 63.0% by weight

(2) Al₂O₃: 19.0 to 23.0% by weight

(3) MgO: 10.0 to 15.0% by weight

(4) CaO: 4.0 to 11.0% by weight

(5) The total of the above (1) to (4): 99.5% by weight or higher

The glass fiber according to the present embodiment, since having theabove composition, can have a sufficiently broadened working temperaturerange in the production from the glass composition, and can become onehaving an elastic modulus equal to that of S glass. Specifically, whilethe 1,000-poise temperature can be made 1,385° C. or lower (typically1,350° C. or lower), and the working temperature range is securedsufficiently (typically 40° C. or higher), the glass fiber having ashigh an elastic modulus as of about 95 GPa or higher (typically 97 to 98GPa) can efficiently be provided.

If the SiO₂ content is 57.0% by weight or higher based on the totalweight of the composition of the glass fiber, the mechanical strength asthe glass fiber can be improved, and the glass fiber is chemicallystable. On the other hand, if the content is 63.0% by weight or lower,since the 1,000-poise temperature and the liquid phase temperaturedecrease, the production of the glass fiber is easy. Particularly inorder to make the 1,000-poise temperature 1,350° C. or lower, the SiO₂content is preferably 57.5 to 62.0% by weight, and more preferably 58.0to 61.0% by weight, based on the total weight of the composition of theglass fiber.

The case where the Al₂O₃ content is 190% by weight or higher based onthe total weight of the composition of the glass fiber can raise theelastic modulus. On the other hand, the case where the content is 23.0%by weight or lower, since the liquid phase temperature decreases, canbroaden the working temperature range. The Al₂O₃ content is preferably19.5 to 22.0% by weight, and more preferably 20.0 to 21.0% by weight,based on the total weight of the composition of the glass fiber.

The case where the MgO content is 10.0% by weight or higher based on thetotal weight of the composition of the glass fiber can raise the elasticmodulus of the glass fiber. On the other hand, the case where thecontent is 15.0% by weight or lower, since the liquid phase temperaturedecreases, can broaden the working temperature range. The MgO content ispreferably 11.0 to 14.0% by weight, and more preferably 11.5 to 13.0% byweight, based on the total weight of the composition of the glass fiber.

If the CaO content is 4.0 to 11.0% by weight based on the total weightof the composition of the glass fiber, the production of the glass fiberis easy. That is, the case where the CaO content is 4.0% by weight orhigher based on the total weight of the composition of the glass fiber,since the liquid phase temperature decreases, can broaden the workingtemperature range. On the other hand, the case where the content is11.0% by weight or lower can reduce the 1,000-poise temperature and theliquid phase temperature. If the CaO content becomes 11.0% by weight orhigher, since the liquid phase temperature of the glass compositionbecomes high in some cases, the CaO content is preferably 5.5 to 10.5%by weight, and more preferably 7.0 to 10.0% by weight, based on thetotal weight of the composition of the glass fiber.

In the case where the total content of SiO₂, Al₂O₃, MgO and CaO is lowerthan 99.5% by weight based on the total weight of the composition of theglass fiber, since the content of other impurity components becomesrelatively high, the working temperature range in the production of theglass fiber and the elastic modulus of the glass fiber obtained cannotbe secured. Therefore, the above total content is preferably 99.7% byweight or higher, and more preferably 99.8% by weight, based on thetotal weight of the composition of the glass fiber.

In the composition of the glass fiber, the total content (A+B) of theSiO₂ content (as A) and the Al₂O₃ content (as B) is preferably 77.0 to85.0% by weight, and more preferably 78.0 to 82.0% by weight. If A+B is85.0% by weight or lower, the melt temperature of the glass can belowered sufficiently, and spinning is easily carried out. On the otherhand, if A+B is 77.0% by weight or higher, since the devitrificationphenomenon of deposition of crystals in the glass hardly occurs,spinning in the production of the glass fiber becomes easy. In order tomake the 1,000-poise temperature 1,350° C. or lower. A+B is preferably81.0% by weight or lower. Further in order to make the liquid phasetemperature 1,300° C. or lower, A+B is preferably 80.0% by weight orlower.

In the composition of the glass fiber, the weight ratio of the SiO₂content/the Al₂O₃ content (taken as A/B) is preferably 27 to 3.2, andmore preferably 2.9 to 3.1. If A/B is 3.2 or lower, the glass fiberhaving a high elastic modulus can be obtained. On the other hand, if theweight ratio is 2.7 or higher, the liquid phase temperature can bereduced, and the devitrification phenomenon can be suppressed.

In the composition of the glass fiber, the total content (C+D) of theMgO content (as C) and the CaO content (as D) is preferably 16.0% byweight or higher. In the case where C+D is 16.0% by weight or higher,since the 1,000-poise temperature and the liquid phase temperature canbe reduced, and additionally, the glass composition is easily melted andthe viscosity can be reduced, the production of the glass fiber becomeseasy. Therefore, (C+D) is more preferably 18.0% by weight or higher.

In the composition of the glass fiber, the weight ratio of the MgOcontent/the CaO content (taken as C/D) is preferably 0.8 to 2.0, andmore preferably 1.0 to 1.8. If C/D is 2.0 or lower, since the liquidphase temperature decreases, the working temperature range can bebroadened, and the working temperature range can be secured, forexample, by 40° C. or higher. On the other hand, if C/D is 0.8 orhigher, the elastic modulus of the glass fiber obtained can be raised.

As described above, according to findings now newly found by the presentinventors, the speed of the devitrification of the glass containingSiO₂, Al₂O₃, MgO and CaO is influenced by the kind of thedevitrification primary phase. That is, in the case where thedevitrification primary phase is a cordierite crystal or a mixed crystalof cordierite and anorthite, crystals hardly deposit at the liquid phasetemperature as compared with the ease of other crystals. Therefore, inthe case of spinning a molten glass of this composition, occurrence oftrouble including cutting in the production of the glass fiber can besuppressed, allowing stable spinning.

From such a viewpoint the glass fiber according to the presentembodiment preferably has a composition in which the three componentsSiO₂, MgO and CaO in constituents of the glass fiber satisfy thecondition being in the range surrounded by coordinate points describedbelow in a three-component phase diagram represented by coordinates((a), (b), (c)) in which (a) the SiO₂ content/(the SiO₂ content+the MgOcontent+the CaO content)×100, (b) the MgO content/(the SiO₂ contentof+the MgO content+the CaO content)×100, and (c) the CaO content/(theSiO₂ content+the MgO content+the CaO content)×100 are taken asrespective coordinates, the coordinate points being ((a)=81.0, (b)=19.0,(c)=0.0), ((a)=71.0, (b)=29.0, (c)=0.0), ((a)=71.0, (b)=15.0, (c)=14.0)and ((a)=81.0, (b)=8.0, (c)=11.0). In the case where the Al₂O₃ contentis 19.0 to 23.0% by weight, particularly nearly 20% by weight, since ina glass composition for the glass fiber having such a composition, thedevitrification primary phase forms a cordierite crystal or a mixedcrystal of cordierite and anorthite, the glass composition isadvantageous further for the production of the glass fiber.

In the case where Al₂O₃ is lower than 19.0% by weight, in thethree-component phase diagram of SiO₂, MgO and CaO, the devitrificationprimary phase does not form a cordierite crystal or a mixed crystal ofcordierite and anorthite in some cases. In order for the devitrificationprimary phase to form a cordierite crystal, the Al₂O₃ content based onthe total weight is preferably 19.5% by weight or higher.

The glass fiber according to the present embodiment is more preferablymade to have a composition in which the devitrification primary phaseforms a cordierite crystal or a mixed crystal of cordierite andanorthite, provided that the contents of SiO₂, MgO, CaO and Al₂O₃ aremade to be under the above-mentioned condition. Here, the composition inwhich the devitrification primary phase forms a cordierite crystal or amixed crystal of cordierite and anorthite will be described hereinafter.FIG. 1 is a composition diagram showing compositions of the threecomponents SiO₂, MgO and CaO of glass fibers. A point X in FIG. 1 is apoint indicating (SiO₂, MgO, CaO)=(81.0% by weight, 19.0% by weight,0.0% by weight); and a point Y is a point indicating (SiO₂, MgO,CaO)=(71.0% by weight, 29.0% by weight, 0.0% by weight). Further a pointZ is a point indicating (SiO₂, MgO, CaO)=(71.0% by weight, 15.0% byweight, 14.0% by weight); and a point W is a point indicating (SiO₂,MgO, CaO)=(81.0% by weight, 8.0% by weight, 11.0% by weight). That is,the compositions in which the devitrification primary phase forms acordierite crystal or a mixed crystal of cordierite and anorthitesatisfy the condition being in the tetragonal range surrounded by thepoints X, Y, Z and W.

Here, % by weight of each component in the above points X, Y, Z and Windicates the content of the each component based on 100% by weight ofthe total of the three components SiO₂, MgO and CaO. However, since thecomposition of the glass fiber contains at least Al₂O₃ as a componentother than SiO₂, MgO and CaO, the content of each component shown inFIG. 1 is different from an actual content.

In a composition of the glass fiber, for example, in the case where theAl₂O₃ content is 20.0% by weight based on the total weight contents ofSiO₂, MgO and CaO in an actual composition of a glass fiber of eachcomponent at the points X, Y, Z and W become the numerical valuesdescribed above multiplied by 0.8. FIG. 2 is a composition diagramshowing compositions of the three components SiO₂, MgO and CaO in thecase where Al₂O₃ is 20.0% by weight based on the total weight.Specifically, the composition of the glass fiber, based on the totalweight of the composition of the glass fiber, satisfies the conditionbeing in the range surrounded by the points X, Y, Z, W and V, in whichthe Al₂O₃ content is 20.0% by weight; the SiO₂ content is 56.8 to 64.8%by weight; the MgO content is 6.4 to 23.2% by weight; and the CaOcontent is 0.0 to 11.2% by weight. The region of the composition of theabove three components in this composition diagram varies depending onthe Al₂O₃ content.

The composition of the glass fiber according to the present embodimentbasically contains SiO₂, MgO, CaO and Al₂O₃, and has the above-mentionedcharacteristic composition, but may further contain other components,for example, by inevitable mingling of substances contained in rawmaterials of each component. The other components include alkali metaloxides such as Na₂O, and Fe₂O₃, Na₂O, TiO₂, include alkali metal oxidessuch as Na₂O, and Fe₂O₃, Na₂O, TiO₂, ZrO₂, MoO₂ and Cr₂O₃. These othercomponents may be contained in lower than 0.5% by weight, preferably inlower than 0.3% by weight, and more preferably in lower than 0.2% byweight.

In the glass fiber according to the present embodiment, for fineregulation and the like of the glass composition to achieve particularlyboth the mechanical strength and the improvement of spinnability, Fe₂O₃and an alkali metal oxide may be contained in 0.4% by weight or less intotal, and preferably in 0.01% by weight or more and less than 0.3%) byweight. In this case, the Fe₂O₃ content is preferably 0.01% by weight ormore and less than 0.3% by weight, and more preferably 0.03%) by weightor more and less than 0.2% by weight.

The above glass fiber can be produced from the glass composition. Theglass fiber may take any form of a monofilament of the glass fiber, aglass fiber strand composed of a plurality of glass fiber monofilaments,and a glass fiber yarn obtained by twisting the glass fiber strand. Thefiber diameter of the monofilament of the glass fiber may be, forexample, 3 to 30 μm, and the glass fiber strand can be obtained bycollecting, for example, 50 to 8,000 of the monofilaments. The glassfiber yarn can be produced by giving, for example, 13 or less-timestwists/25-mm to the glass fiber strand. The glass fiber may be providedas a wound thread body in which about 10 to 200 km of the glass fiber iswound on the periphery of a paper- or plastic-made core material, or maybe provided as glass fibers cut into about 1 inch (glass fiber choppedstrand or the like). By using the glass fiber according to the presentembodiment, the glass fiber may be provided as a woven fabric, knittedfabric, nonwoven fabric, mat, braid, roving, powder and the like of theglass fiber. The glass fiber according to the present embodiment may beused singly, but may be used in combination with one or more of a knowncommercially available glass fiber, carbon fiber, aramid fiber, ceramicfiber and the like.

As a method for producing the glass fiber, a known method such as theremelting method and the direct melting method can be employed. In theseknown methods, usually, a molten glass composition is drawn out fromseveral hundreds to several thousands of platinum nozzles at a highspeed to be fiberized to thereby obtain a glass fiber.

Meanwhile, the cross-sectional shape of the glass fiber according to thepresent embodiment may be not only a usual circular shape but also aflat cross-sectional fiber such as of an elliptical, oval orcocoon-shape type, or a profile cross-sectional fiber such as of astar-shape, hexagonal or triangular type. Particularly in the case wherethe glass fiber is a flat cross-sectional fiber or a profilecross-sectional fiber, spinning needs to be carried out in a relativelyhigh viscosity. Therefore, if the composition is one in which thedevitrification primary phase of the glass forms a cordierite crystal ora mixed crystal of cordierite and anorthite, crystals of the moltenglass hardly deposit even in a high viscosity, that is, at a lowtemperature, allowing stable production of the glass fiber.

That is, in the case where the glass fiber is a flat cross-sectionalfiber or a profile cross-sectional fiber, in order that the glass fiberis easily produced and has a sufficient elastic modulus, the following(1) and (2) conditions are preferably satisfied. Further in order tospin the glass fiber more stably, the following (3) condition ispreferably satisfied.

(1) Based on the total weight of the composition of the glass fiber, thecontent of SiO₂ is 57.0 to 63.0% by weight; the content of Al₂O₃ is 19.0to 23.0% by weight; the MgO content is 10.0 to 15.0% by weight; and theCaO content is 4.0 to 11.0% by weight.

(2) The total of the contents of SiO₂, Al₂O₃, MgO and CaO is 99.5% byweight or higher.

(3) The three components SiO₂, MgO and CaO have a composition satisfyingthe condition being in the range surrounded by coordinate pointsdescribed below in a three-component phase diagram represented bycoordinates ((a), (b), (c)) in which (a) the SiO₂ content/(the SiO₂content+the MgO content+the CaO content)×100, (b) the MgO content/(theSiO₂ content+the MgO content+the CaO content)×100, and (c) the CaOcontent/(the SiO₂ content+the MgO content+the CaO content)×100 are takenas respective coordinates, the coordinate points being ((a)=81.0,(b)=19.0, (c)=0.0), ((a)=71.0, (b)=29.0, (c)=0.0), ((a)=71.0, (b)=15.0,(c)=14.0) and ((a)=81.0, (b)=8.0, (c)=11.0).

In a flat cross-sectional fiber and a profile cross-sectional fiber, thereduced fiber diameter is preferably 3 to 30 μm, and more preferably 5to 20 μm. Particularly in a flat cross-sectional fiber, the flatnessratio is preferably 2 to 8, and more preferably 3 to 7. Here the reducedfiber diameter refers to a diameter of a circular cross-sectional fiberhaving the same fiber cross-sectional area, and the flatness ratiorefers to a ratio (a long side/a short side) of the long side and theshort side of a rectangle when the rectangle circumscribing the glassfiber cross-section and having a minimum area is assumed.

The glass fiber obtained by the above-mentioned method can be applied tovarious types of applications. The glass fiber can be applied, forexample, to glass fibers for FRP and FRTP used in industrial materialsand car parts materials, and glass fiber-reinforced materials oflaminates for printed wiring boards being electronic materials.

Glass fiber composite materials can be produced by using reinforcingmaterials (matrix resins) with the glass fiber according to the presentembodiment. A method for producing a glass fiber composite materialdepends on a matrix resin to be used. In the case of using athermoplastic resin, a glass fiber composite material can be produced bya technique such as a stampable sheet molding method, an injectionmolding method and an infusion method. Examples of thermoplastic reinsusable are polyethylene resins, polypropylene resins, polystyreneresins, acrylonitrile/butadiene/styrene (ABS) resins, methacrylicresins, vinyl chloride resins, polyamide resins, polyacetal resins,polyethylene terephthalate (PET) resins, polybutylene terephthalate(PBT) resins, polycarbonate resins, polyphenylene sulfide (PPS) resins,polyether ether ketone (PEEK) resins, liquid crystal polymer (LCP)resins, fluororesins, polyether imide (PEI) resins, polyarylate (PAR)resins, polysulfone (PSF) resins, polyether sulfone (PES) resins andpolyamide-imide (PAI) resins.

On the other hand, in the case of using, as a matrix resin for a glassfiber composite material, a thermosetting resin such as an unsaturatedpolyester resin, a vinyl ester resin, an epoxy resin, a melamine resinor a phenol resin, a production method can be employed such as a handlay-up method, a spray-up method, a resin transfer molding (RTM) method,a sheet molding compound (SMS) method, a bulk molding compound (BMC)method, a protrusion method, a filament winding method or an infusionmethod.

In glass fiber composite materials, as reinforcing materials other thanmatrix resins, usable are a cement, mortar, concrete, asphalt, metal,carbon, ceramic, natural rubber, synthetic rubber and the like.

Glass fiber composite materials using the glass fiber can be used asmaterials for various types of applications as described below. Forexample, in aircraft equipment applications, the glass fiber compositematerials can be used for base materials for aircrafts, interiortrimming materials, vibration-proof materials and the like, and invehicle-related applications, they can be used for damping-reinforcingmaterials, bumpers, engine undercovers, fenders, roof materials, bodies,spoilers, muffler filters, dash panels, radiators, timing belts, and thelike. In marine vessel-related applications, they can be used formotorboats, sailboats, fishing boats, and the like; in construction,engineering works and building-material-related applications, for facedwalls, luminous ceilings and illumination covers, front face liningcloths, insect nets, roll blinds, film materials for tents, backlitsignboards, corrugated panels, flat plates and folded plates forlighting, concrete-anticorrosive and -reinforcing materials, outer wallreinforcing materials, waterproof coating materials, smokeproof hangingwalls, nonflammable transparent partitions, screen films, roadreinforcing materials, bath tubs, bath and toilet units, and the like;and in leisure and sports-related applications, for fishing rods, tennisrackets, golf clubs, skiing boards, helmets, and the like. Further inelectronic device-related applications, they are used forprinted-circuit boards, electric insulating boards, terminal boards,substrates for ICs, electronic apparatus-housing materials, packagematerials for electronic components, optical apparatus-housingmaterials, package materials for optical components, insulatingsupporters, and the like; in industrial facility-related applications,for windmill blades, glass filter bags, outer shell materials ofnonflammable heat-insulating materials, reinforcing materials ofresinoid grindstones, aluminum-filtration filters, and the like; and inagriculture-related applications, for vinyl houses, poles foragriculture, silo tanks, and the like. The above-mentioned glass fibercomposite materials can be used also as reinforcing materials of knownfiber-reinforced composite materials.

EXAMPLES

Hereinafter, preferable Examples according to the present invention willbe described in more detail, but the present invention is not limited tothese Examples.

[Preparation and Evaluation of Glass Compositions for the Glass Fiber]

Glass raw materials were formulated so as to make compositions shown inTables 1, 2 and 3, and glass compositions having the compositionscontaining SiO₂ (A), Al₂O₃ (B), MgO (C) and CaO (D) as basiccompositions were melt spun to thereby obtain glass fibers having afiber diameter of 13 μm. The obtained glass fibers had the samecomposition as the glass composition of the raw material. Then, for eachglass fiber, the 1,000-poise temperature, the liquid phase temperatureand the working temperature range in the production were determined; thedevitrification resistance was evaluated and crystals of thedevitrification primary phase were analyzed; and the elastic modulus ofthe glass fiber obtained finally was measured. The acquired results areshown in Tables 1, 2 and 3 together with the compositions. Thesecharacteristics were determined by the following evaluation methods.

(1) The 1,000-poise temperature: a glass of each glass compositionmelted in a platinum crucible was continuously measured for theviscosity while the melt temperature of the glass was being varied, byusing a rotary B-type viscometer; and a temperature corresponding to oneat which the viscosity was 1,000 poises was defined as a 1,000-poisetemperature. The viscosity was measured according to JIS Z8803-1991.(2) The liquid phase temperature: a crushed material of a glass of eachglass composition was put in a platinum boat, and heated in a tubularelectric oven provided with a temperature gradient of 1,000° C. to1,500° C. A temperature at which crystals started to deposit was definedas a liquid phase temperature.(3) The working temperature range: the working temperature range wascalculated from (the 1,000-poise temperature)−(the liquid phasetemperature).(4) The elastic modulus: the elastic modulus was measured by anultrasonic method. Ultrasonic waves (longitudinal wave sonic velocity,transverse wave sonic velocity) transmitting through a glass bulk weremeasured, and the elastic modulus was calculated from a specific gravityof the glass, and values of the longitudinal wave sonic velocity and thetransverse wave sonic velocity.(5) The evaluation of the devitrification resistance: each glasscomposition was melted at the 1,000-poise temperature or higher, andthereafter, allowed to stand at a temperature lower by 150° C.±50° C.than the liquid phase temperature for 6 hours. Then, the situation ofcrystals developing on the surface or the interior of the glasscomposition was observed, and evaluated in three stages. A indicatesthat no crystal deposited; B indicates that crystals deposited at a partof the surface; and C indicates that crystals deposited on the surfaceand the interior.(6) The kinds of crystals of the devitrification primary phase: thesample measured for the liquid phase temperature was used, and thedepositing crystal primary phase part was crushed and analyzed by anX-ray diffractometer to thereby identity the kinds of the crystals. Thekinds of crystals of the devitrification primary phases in Tables 1 to 3are according to the following description. In Tables, the case wheretwo or more kinds of crystals are shown indicates that the coexistenceof both crystal kinds was confirmed.COR: CordieriteANO: AnorthitePYR: PyroxeneMUL: MulliteTRI: TridymiteSPI: SpinelFOR: ForsteriteCRI: CristobaliteCAS: Calcium Aluminium Silicate

Samples 1 to 19 shown in Table 1 corresponded to respective Examples;and Samples 20 to 44 shown in Tables 2 and 3 corresponded in respectiveComparative Examples. Further, Samples 36 to 39 in Table 3 correspondedto the glass compositions in examples 2 to 5 shown in Japanese ExaminedPatent Application Publication No. 62-001337, Samples 40 to 44 in Table3 corresponded to the glass compositions in examples 1, 4, 7, 14 and 15shown in Japanese Unexamined Patent Application Publication No.2009-514773, respectively.

Further, molten glasses of the compositions in Examples 5 and 9 werespun to thereby obtain flat cross-sectional glass fibers having an ovalcross-sectional shape having a reduced fiber diameter of 15 μm and aflatness ratio of 4. As a result, both the Samples were confirmed toexhibit excellent spinning workability.

TABLE 1 Composition (wt %) Sample Physical Properties 1 2 3 4 5 6 7 8 910 SiO₂(A) 60.2 60.2 60.2 60.1 58.1 58.1 58.7 59.1 58.7 58.2 Al₂O₃(B)21.1 20.1 20.1 20.1 20.1 20.1 20.1 20.1 20.6 21.1 MgO(C) 12.1 13.1 12.110.1 12.1 13.1 12.6 12.1 12.1 12.1 CaO(D) 6.6 6.5 7.5 9.5 9.5 8.5 8.58.5 8.5 8.5 Fe₂O₃ 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Na₂O 0.0 0.10.1 0.1 0.1 0.1 0.0 0.1 0.0 0.0 Liquid Phase Temperature (° C.) 13051286 1271 1238 1223 1241 1241 1254 1246 1268 1,000-poise Temperature (°C.) 1346 1331 1338 1343 1302 1301 1311 1322 1318 1314 WorkingTemperature Range (° C.) 41 45 67 105 79 60 70 68 72 46 Elastic Modulus(GPa) 98 97 96 95 98 98 98 97 97 98 Devitrification Resistance A A A A BA A A A A Devitrification Primary Phase COR COR COR COR COR COR COR CORCOR COR ANO ANO ANO ANO ANO Composition (wt %) Sample PhysicalProperties 11 12 13 14 15 16 17 18 19 SiO₃(A) 58.1 59.2 59.1 59.1 62.261.2 58.2 58.6 58.6 Al₂O₃(B) 20.6 20.1 21.1 20.1 21.1 21.1 20.6 20.620.6 MgO(C) 12.6 12.6 12.1 13.1 12.1 12.1 12.1 11.6 12.6 CaO(D) 8.5 8.07.5 7.5 4.6 5.6 9.0 9.0 8.0 Fe₂O₃ 0.1 0.0 0.1 0.1 0.0 0.0 0.1 0.1 0.1Na₂O 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.1 0.1 Liquid Phase Temperature (° C.)1262 1262 1286 1262 1357 1325 1242 1249 1259 1,000-poise Temperature (°C.) 1308 1319 1330 1317 1381 1359 1315 1321 1316 Working TemperatureRange (° C.) 46 57 44 55 24 34 73 72 57 Elastic Modulus (GPa) 98 97 9798 96 97 98 97 98 Devitrification Resistance A A A A A A A A ADevitrification Primary Phase COR COR COR COR COR COR COR COR COR ANOANO ANO

TABLE 2 Composition (wt %) Sample Physical Properties 20 21 22 23 24 2526 27 28 SiO₂(A) 62.1 60.1 60.2 64.9 58.0 55.1 60.2 65.2 60.2 Al₂O₃(B)18.1 18.1 18.1 24.9 24.0 15.1 15.1 15.1 15.1 MgO(C) 15.1 14.1 14.6 9.96.0 15.1 15.1 10.1 5.1 CaO(D) 4.5 7.5 7.0 0.0 12.0 14.5 9.5 9.6 19.6Fe₂O₃ 0.1 0.1 0.1 0.3 0.0 0.1 0.0 0.0 0.0 Na₂O 0.1 0.1 0.0 0.0 0.0 0.10.1 0.0 0.0 Liquid Phase Temperature (° C.) 1289 1268 1271 1465 13601261 1300 1316 1184 1,000-poise Temperature (° C.) 1337 1310 1303 14701373 1200 1279 1386 1332 Working Temperature Range (° C.) 48 42 32 5 13−61 −21 70 148 Elastic Modulus (GPa) 98 98 98 95 94 100 99 92 91Devitrification Resistance C C C C C C C A A Devitrification PrimaryPhase COR PYR PYR MUL ANO ANO PYR CRI CAS PYR Composition (wt %) SamplePhysical Properties 29 30 31 32 33 34 35 SiO₂(A) 55.1 50.1 40.2 60.155.1 50.2 60.1 Al₂O₃(B) 15.1 20.1 20.1 25.1 25.1 25.1 18.1 MgO(C) 20.120.1 20.1 10.1 5.1 15.1 15.1 CaO(D) 9.6 9.6 19.6 4.6 14.6 9.6 6.6 Fe₂O₃0.0 0.0 0.0 0.0 0.0 0.0 0.1 Na₂O 0.1 0.1 0.0 0.1 0.1 0.0 0.0 LiquidPhase Temperature (° C.) 1378 1363 >1400 1382 >1400 1295 12941,000-poise Temperature (° C.) 1175 1138 979 1392 1338 1207 1305 WorkingTemperature Range (° C.) −203 −225 — 10 — −88 11 Elastic Modulus (GPa)104 107 112 97 96 105 98 Devitrification Resistance C C C A C C CDevitrification Primary Phase FOR FOR SPI COR ANO SPI COR PYR FOR PYR

TABLE 3 Composition (wt %) Sample physical Properties 36 37 38 39 40 4142 43 44 SiO₂(A) 48.0 54.0 67.0 55.0 62.6 63.0 62.3 65.0 64.0 Al₂O₃(B)28.0 34.0 21.0 24.0 18.5 20.0 17.3 15.0 20.0 MgO(C) 16.0 4.0 4.0 5.0 9.511.3 8.0 6.0 11.0 CaO(D) 8.0 8.0 8.0 16.0 8.5 4.8 11.6 14.0 4.0 Fe₂O₃0.0 0.0 0.0 0.0 0.2 0.2 0.2 0.0 0.0 Na₂O 0.0 0.0 0.0 0.0 0.7 0.7 0.7 0.01.0 Liquid Phase Temperature (° C.) 1390 1397 1313 1318 1238 1279 12611301 1316 1,000-poise Temperature (° C.) 1196 1405 1501 1330 1366 13791348 1376 1398 Working Temperature Range (° C.) −194 8 188 12 128 100 8775 82 Elastic Modulus (GPa) 107 98 89 96 93 95 92 90 94 DevitrificationResistance C C A C A A B A A Devitrification Primary Phase SPI MUL ANOANO ANO COR ANO ANO COR COR CAS CAS CAS CAS CAS

As shown in Tables 1 to 3, it is confirmed that Samples 1 to 19 beingExamples exhibited broad working temperature ranges while exhibitingboth low 1,000-poise temperatures and low liquid phase temperatures, andfurthermore exhibited high elastic moduli, as compared with Samples 20to 44 being Comparative Examples.

The invention claimed is:
 1. A glass fiber, comprising: a SiO₂ contentof 57.0 to 63.0% by weight; a Al₂O₃ content of 19.0 to 23.0% by weight;a MgO content of 10.0 to 15.0% by weight; and a CaO content of 5.5 to11.0% by weight, and a total content of SiO₂, Al₂O₃, MgO and CaO of99.5% by weight or higher based on a total weight thereof, a weightratio of the SiO₂ content/the Al₂O₃ content of 2.7 to 3.2, and a weightratio of the MgO content/the CaO content of 0.8 to 2.0, wherein whereinthe SiO₂ content/(the SiO₂ content+the MgO content+the CaO content)×100is 71.0 or more and 81.0 or less, a devitrification primary phase of theglass is a cordierite crystal or a mixed crystal of cordierite andanorthite, and the glass fiber has an elastic modulus of 95 GPa orhigher.
 2. The glass fiber according to claim 1, comprising: a totalcontent of the SiO₂ content and the Al₂O₃ content of 77.0 to 85.0% byweight.
 3. The glass fiber according to claim 1, comprising: a totalcontent of the MgO content and the CaO content of 16.0% by weight orhigher.
 4. The glass fiber according to claim 1, comprising: a SiO₂content of 57.0 to 62.0% by weight.
 5. The glass fiber according toclaim 4, comprising: a weight ratio of the SiO₂ content/the Al₂O₃content of 2.7 to 3.1.
 6. The glass fiber according to claim 5,comprising: a total content of the SiO₂ content and the Al₂O₃ content of77.0 to 85.0% by weight.
 7. The glass fiber according to claim 5,comprising: a total content of the MgO content and the CaO content of16.0% by weight or higher.
 8. The glass fiber according to claim 5,further comprising a Fe₂O₃ and an alkali metal oxide, and a totalcontent of the Fe₂O₃ content and the alkali metal oxide content of 0.4%by weight or less.
 9. The glass fiber according to claim 4, comprising:a total content of the SiO₂ content and the Al₂O₃ content of 77.0 to85.0% by weight.
 10. The glass fiber according to claim 9, comprising: atotal content of the MgO content and the CaO content of 16.0% by weightor higher.
 11. The glass fiber according to claim 9, further comprisinga Fe₂O₃ and an alkali metal oxide, and a total content of the Fe₂O₃content and the alkali metal oxide content of 0.4% by weight or less.12. The glass fiber according to claim 4, comprising: a total content ofthe MgO content and the CaO content of 16.0% by weight or higher. 13.The glass fiber according to claim 12, further comprising a Fe₂O₃ and analkali metal oxide, and a total content of the Fe₂O₃ content and thealkali metal oxide content of 0.4% by weight or less.
 14. The glassfiber according to claim 4, further comprising a Fe₂O₃ and an alkalimetal oxide, and a total content of the Fe₂O₃ content and the alkalimetal oxide content of 0.4% by weight or less.
 15. The glass fiberaccording to claim 1, comprising: a weight ratio of the SiO₂ content/theAl₂O₃ content of 2.7 to 3.1.
 16. The glass fiber according to claim 1,further comprising a Fe₂O₃ and an alkali metal oxide, and a totalcontent of the Fe₂O₃ content and the alkali metal oxide content of 0.4%by weight or less.
 17. The glass fiber according to claim 1, furthercomprising a Fe₂O₃ and an alkali metal oxide, and the glass fibercomprises a SiO₂ content of 57.0 to 60.2% by weight; a weight ratio ofthe SiO₂ content/the Al₂O₃ content of 2.7 to 3.1; a weight ratio of theMgO content/the CaO content of 1.0 to 1.8; and a total content of theFe₂O₃ content and the alkali metal oxide content of 0.01% by weight ormore and 0.4% by weight or less.
 18. The glass fiber according to claim17, comprising a Al₂O₃ content of 20.1 to 23.0% by weight.
 19. The glassfiber according to claim 1, wherein the total content of SiO₂, Al₂O₃,MgO and CaO is 99.7% by weight or higher based on a total weightthereof.
 20. The glass fiber according to claim 1, wherein the totalcontent of SiO₂, Al₂O₃, MgO and CaO is 99.8% by weight or higher basedon a total weight thereof.
 21. The glass fiber according to claim 1,wherein the MgO content/(the SiO₂ content+the MgO content+the CaOcontent)×100 is 11.9 or more and 19.4 or less.
 22. The glass fiberaccording to claim 1, wherein the CaO content/(the SiO₂ content+the MgOcontent+the CaO content)×100 is 6.59 or more and 14.0 or less.
 23. Theglass fiber according to claim 1, wherein the glass fiber has an elasticmodulus of 96 GPa or higher.
 24. The glass fiber according to claim 1,wherein the glass fiber has an elastic modulus from 97 GPa to 98 GPa.